At present, the spinal fusion technology has obtained a good curative effect on treating neck and waist pain, and cervical vertebra and lumbar vertebra instability, with a fusion rate above 90%. However, many studies have shown that accelerated adjacent segment degeneration, fixation failure, pseudoarticulation formation or other complications may occur after rigid internal fixation or spinal fusion. For this reason, spine dynamic stabilization is becoming a hot technology for treating retrograde degeneration of cervical vertebra and lumbar vertebrae in recent years, and is one of the important developing trends of spine surgery, including five types, such as artificial or total disc replacement, artificial nucleus replacement, transpedicular dynamic neutralization system, interspinous dynamic stabilization device and facet joint formation device. Among these technologies, the interspinous dynamic stabilization device may be minimally invasive during implantation, with highest safety and simplest operation, and may cause minor complications, if any. That is, even if it fails, further surgery may not be influenced. As such, interspinous dynamic stabilization devices have been developing rapidly in recent years.
The implantation of an interspinous dynamic stabilization device has the following advantages. The device may be dynamically stabilized without reducing the immediate stability of the spine, and may disperse the load transmission of the rigid internal fixation to avoid stress shielding. The distraction force of intervertebral distraction may generate an opposite kyphosis on the surgical segment, to expand the inflected ligamenta flava reversedly to reduce the intrusion into the spinal canal, increasing the spinal canal volume. The device may also restore the height of intervertebral space, increase the cross-sectional area of the spinal canal and the opening area of the intervertebral foramen, increase the load of the annulus fibrosus after unloading, reduce the load of the facet joint on the corresponding segment. In addition, with this device, the patient may recover quickly after surgery, with a low recurrence rate, and the symptom such as pain may be significantly relieved, so that the patient may get out of bed earlier to resume normal activities.
However, there are still many defects in the traditional interspinous dynamic stabilization device. For example, the devices may not match the spinous anatomy, hit the spine to cause wear, or be quite complicated in structure. And the traditional device may be too large that the wound during surgery is large and the device is difficult to install and take up much space in the body after operation. In addition, there is a risk of disengagement when the traditional device is stabilized by an assembly, and there is a risk of loosening when the traditional device is stabilized by a binding belt. During the installation of the traditional device, the prosthesis may be required to be close to the spinal dura mater, which increases the surgical difficulty and risk of damaging the spinal dura mater. Further, the elastic structure in the traditional device may show poor elasticity and poor vertical support, and the traditional device has a weak ability of elasticity attenuation resistance after the operation, so it is difficult to ensure low incidence of complications and good long-term effect.
For example, the Coflex system designed and developed by Samani et al. in 1994 is U-shaped when viewed from the side, upper and lower ends of the U-shaped main structure having two “clamp-shaped” fixed wings (in which one is anterior, and the other is posterior) for clamping and fastening upper and lower spinous processes. However, the part of the system to be fastened to the spinous process is a square structure which does not match the spinous anatomy of the spinous process, and in this case, the side wings should be stretched and deformed greatly with a forceps during the surgery, and the side wings should be shut together after the surgery, so the installation of such system is complicated, and the side wings are easy to be fatigue and broken. In addition, such system may only provide sagittal extension and flexion. Chinese Patent No. 201020247832.0 discloses a “spinal nonfusion stabilization device” with substantially the same configuration as the Coflex system. Specifically, in this device, the U-shaped part 1 corresponds to the U-shaped main structure in the Coflex system, front and back fixation plates 2 corresponds to the two “clamp-shaped” fixed wings in the Coflex system, and the front and back fixation plates 2 are fastened to two adjacent spinous processes with screws, to achieve the fixation of the U-shaped main structure. However, as mentioned above, such device may only implement sagittal extension and flexion. That is, the size of the opening end of the U-shaped structure may be changed as the deformation of the U-shaped structure, so that the size of the opening end can match the variation in the distance between the spinous processes. Such U-shaped structure shows poor vertical support. In addition, its barb is relatively far away from the bottom of the U-shaped structure, and the location to which the barb is fastened is far away from the root of the spinous process when the bottom of the U-shaped structure is not close to the spinal dura mater, so the fixation effect would be affected.
The applicant of the present application has filed a Chinese patent application No. 201520426702.6, entitled “interspinous stabilization device”. In clinical applications of the device, the prosthesis is unable to be inserted into a depth close to the dura mater during the surgery due to the large size of the device, so the rotation center of the prosthesis is relatively far away from the rotation center of the lumbar spine when the lumbar spine is twisted, that is, when the lumbar spine moves coronal direction. In addition, it is complicated in fixation with screws, and there is risk of the loosening of the screws. Moreover, the lateral mobility of the device is too large, increasing a new destabilizing factor to the lumbar vertebra.
A perfect interspinous dynamic stabilization device should generate permanent, sufficient distraction force at the bottom of the spinous process after implantation, to restore the height of intervertebral space, increase the opening area of the intervertebral foramen, expand the inflected ligamenta flava reversedly to reduce the intrusion into the spinal canal, and increase the volume of the spinal canal, while allowing the spine to maintain good dynamical activities, such as extension and flexion, for a long period of time. However, the previous interspinous dynamic stabilization devices are generally not able to have both good, persistent vertical distraction force and versatile mobility.